During the normal course of heat exchanger operation, it is oftentimes necessary to replace defective heat exchanger tubes. Constant exposure to the combined debilitating effects of high temperatures, vibration, sooting and corrosion eventually take their toll in tubes. As a consequence, various techniques and apparatus have been developed for the removal of the failed tubes.
One common tube pulling method utilizes a hydraulically driven expandable gripping element. The gripping element is initially inserted into the tube to be removed. The element is subsequently radially expanded (usually by the hydraulic means) so that it is tightly wedged against the inner surface of the tube. The tube is then removed by forcibly extracting the combined tube/gripping element assembly from the tube sheet supporting the tube.
A second common method entails the use of a cutting torch to remove the flared portion of the tube extending beyond the tube sheet. After the flare has been cut, the tube is then manually banged out of the tube sheet with hammers and chisels.
Unfortunately, both of the above enumerated methods exhibit drawbacks.
The hydraulic tube pullers have been generally limited to thin gage tubing having maximum diameters of less then one inch.
The cutting torch method has been found to damage the tube sheet. In order to burn the tubes out, a valley is invariably carved into the tube sheet by the torch prior to the removal of the tube. This necessitates the need to lay down a weld bead between the newly installed tube and the tube sheet to build up the damaged tube sheet surface. Moreover, the weld bead then must be subjected to a finishing grinding operation. Obviously, this method requires additional time and effort to be successful.
Clearly, a more expeditious apparatus for removing tubes from tube supporting structures is desirable.